These cars are easy to take apart, it's putting them back together that is tricky!

There are 4 screws that hold the roof to the body shell. Use a long shank #2 Philips driver.

It helps to have a magnetized driver, that way, you have a chance to pull the screws back up the holes. You have to "feel around" a bit for the screws. If the car you are working on has doors you can peek through them to see where you are. The new baggage and RPO cars do not have working end doors, as the body shell is different.

If you drop the screws inside, no worries, just find them when you take off the roof.

The roofs are NOT glued on, but often are assembled while the paint is not cured, and will "stick" a bit. If you pull up on one end of the roof, you can see that there is a tab on the roof that engages the body about halfway down, but NOT in the exact center. A small flat blade screwdriver here can help.

After you have pulled the roof off, any paint stuck to the body can be lightly scraped off.

Here's a diner car opened up:

(Notice that this car has 3 of the 4 possible power connections between roof and body used. why?)

To reassemble, you have 2 problems:

One, any sliding doors are held in by the roof, so you need them to stay in place. Here's my trick:

Be sure to check that the roof seats fully down. If it does not, you do not have the doors up against the body, or the bottoms are not in their groove.

Next trick is getting the screws back in. Make sure you have a magentized screwdriver. Then slowly lower the screw into the hole, and try to orient the car so you can see inside, or use a flashlight. It takes some time.